The first known attempt at radial artery access for angiography was made in March 1947 by Dr. Stig Radner in Lund, Sweden. He reported on his new technique a year later, describing a radial artery cutdown in the upper third of the forearm, after which a 7-Fr to 9-Fr catheter was advanced in a retrograde fashion to perform a thoracic aortogram.1 It was not until over 4 decades later that the radial artery started to be accessed percutaneously, rather than through a cutdown, and for the purpose of cannulating the coronary arteries. In 1989, emboldened by the safety of the radial arterial line for critically ill patients, Dr. Lucien Campeau from Montreal Heart Institute described his experience of accessing the left radial artery for coronary angiography in 100 patients (90 men and 10 women).2 Primarily using a 5-Fr system, he was successful in cannulating the radial artery in 90% of patients, and reported only 2 complications, including a brachial artery dissection and a radial artery occlusion, neither of which were symptomatic. Three years later, in 1992, the first coronary stents were placed in 3 men via the right radial artery by Dr. Ferdinand Kiemeneij in Amsterdam.3 He attributed his ability to do this to “miniaturization” of coronary guiding catheters to 6-Fr and adequate crimping of a Palmaz-Schatz stent on a balloon to allow it to pass without becoming dislodged within the small guide.
Following these successes, the use of radial access spread worldwide. However, the enthusiasm was short-lived in some countries, including the United States, where there was a rise and fall of radial procedures during the 1990s. United States operators quickly grew frustrated by the difficulty in performing a radial procedure compared to the ease of a femoral procedure, in which there were not issues of spasm, tortuous anatomy, or limitations in guide size. By the late 2000s, 50% of percutaneous coronary interventions (PCI) were performed radially in Europe and Canada, and 60% in Japan, but only 1.7% in the United States, putting it on par with the Middle East and Africa.4,5 Around the same time, though, concerns regarding the morbidity and mortality associated with bleeding and vascular complications, the emergence of new radial-specific equipment, and the enthusiasm of young operators who had no memory of the struggles of their predecessors, began to take hold. Within a 6-year period, radial PCI in the United States grew to over 30%, and has not shown signs of stopping (Fig. 22-1). Few interventional fellows in the country now graduate without being proficient in both radial and femoral procedures, and a new paradigm is seen within cardiac catheterization laboratories across the country where patients can ambulate right after their procedure and go home that same day.
Bleeding is the most common complication after PCI. It is independently associated with a 3-fold increase in mortality and major adverse cardiovascular events (MACE)6 and contributes to 12.1% of all in-hospital mortalities after PCI.7 In addition, 2.3% of patients receive a blood transfusion post-PCI, which has also been independently associated with an increased risk of mortality and MACE.8 Although non-access site bleeding has been associated with a worse prognosis than access site bleeding, access site bleeding still carries a 1.7-fold increased risk of mortality compared with no bleeding.9 While femoral access site bleeding and vascular complications have decreased over the past decade, they still occur in ~2% of all PCIs, and women have a >2-fold increased risk compared to men.10,11 Moreover, patients with a particularly high bleeding risk, such as those presenting with ST-segment elevation myocardial infarction (STEMI), have femoral bleeding rates of 5% or more.12,13
Observational studies and randomized controlled trials (RCTs) have consistently demonstrated a reduction in bleeding and vascular complications with radial versus femoral access.5,14-17 In addition, this reduction increases as a patient’s bleeding risk increases, and those with the highest baseline bleeding risk benefit most from a radial approach.18 Similarly, as the baseline bleeding risk increases, there is an increased risk of mortality, and the impact of strategies that reduce bleeding, such as the radial approach, begin to reduce mortality. It has been demonstrated in larger RCTs of STEMI patients that those who have a higher risk of baseline bleeding and mortality do benefit from radial versus femoral access, whereas this has not necessarily been the case in lower-risk cohorts.13,15,16,19
In 2013, there were several studies published evaluating the cost benefit of radial procedures, and all showed very similar results.20-22 They all examined both the periprocedural and postprocedural costs associated with radial versus femoral access. There was no periprocedural cost benefit with radial PCI versus femoral PCI, and, in fact, in the case of a diagnostic catheterization, the cost of radial PCI was slightly higher (likely due to the radial-specific equipment) compared to femoral PCI, when vascular closure devices were rarely used (~10%).21 On the other hand, radial PCI produced a cost savings postprocedurally of $571 to $705 per case. This savings was primarily due to a decreased length of stay rather than bleeding, which accounted for <20% of the savings. The shortened stay was not due to same-day discharge, which was occurring in <5% of the cases. Instead, presumably from early ambulation and recovery, radial patients were able to leave the hospital approximately one third of a day sooner than femoral patients, saving money on bed space and nursing staff. While the amount of money saved per patient seems small, the effect on the health care system is quite large when translated across the country, totaling $50 million or more.20 It is also noteworthy that the largest cost savings from radial PCI comes when employed in patients who were at the highest risk of bleeding ($642 in low risk patients and $1621 in high risk patients). This mirrors the data seen with bleeding and mortality-the higher-risk the patient, the more benefit is gained from a radial procedure.
The data regarding patient satisfaction with radial procedures is limited, but for anyone who does radial procedures, the testimonials given by patients are convincing enough. Still, in an old, but often-cited article, Cooper et al. reported that 80% of patients who had undergone both techniques strongly preferred the radial approach, whereas only 2% preferred the femoral approach.23 Likewise, patients in both RIVAL (Radial Versus Femoral Access for Coronary Intervention) and SAFE-PCI (Study of Access Site for Enhancement of PCI for Women) significantly preferred radial access over femoral access if they were to need to have their procedure again.15,24
One of the biggest challenges of doing radial procedures is getting through the learning curve. It must be remembered that the wrist is not a small groin, and that there are new skills to learn, even for the most adept femoral operator. Becoming proficient at radial procedures is about case volume, not operator status. Therefore, when learning radial approaches, everyone is starting at ground zero, which can be frustrating, particularly for long-standing femoral operators, as well as their staff. Investigations into the initial learning curve have suggested that it takes approximately 50 cases to master the basics. However, as with learning any skill, technical proficiency continues to improve well beyond the initial learning curve, so the more cases one does, the better one gets.25
In a study evaluating the learning curve for diagnostic cases, radial experts (defined as experienced femoral angiographers who had received formal training in radial techniques with >100 previous radial procedures) were compared with radial non-experts (defined as experienced femoral angiographers with basic or no radial experience) at baseline, and then over the course of 12 months as both groups performed radial procedures.26 At baseline, the radial experts had significantly shorter procedural and fluoroscopic times compared with the radial non-experts. By ~36 cases, there was no significant difference in procedural times between the experts and non-experts, but still a difference in fluoroscopic times. By ~63 cases, the procedural and fluoroscopic times between the radial expert and non-expert were no longer appreciably different. Similarly, in operators newly performing radial PCI, the odds of failure decline substantially up to 50 cases, while further decline in failures after 100 cases is small.27 A large analysis tracking new radial operators in the United States also concluded that the threshold to overcome the learning curve is approximately 30 to 50 PCIs.28 In addition, median fluoroscopy times and contrast use decreased significantly with increasing radial volume, and despite operators doing more complex radial procedures, as their experience grew, procedure success remained consistently high.
There are several ways to approach one’s learning curve. To begin with, operators can start on their own, or the entire cardiac catheterization laboratory can change together. The latter may be more logistically difficult in the beginning, but likely results in more efficiency in the end.29 Operators can also choose to start with easy cases, gradually increasing to more complex cases as their comfort and skill level grows, or they can take a “radial-first” approach from the start. A rapid transition to a radial-first approach is likely best. Many operators get stuck in their learning curve, tending to favor the radial approach in stable male patients, whereas the patients most likely to benefit, due to higher risk of bleeding and vascular complications, are older, female, and unstable patients, particularly those with STEMI.30 This avoidance of the radial approach in potentially more challenging cases has created a risk–treatment paradox in the United States, whereby the patients who are most expected to benefit from a radial procedure are the least likely to receive it. Consequently, it is encouraged that operators complete their learning curve, pushing themselves to do more radial procedures and to get comfortable with all types of patients. It has been shown that as radial PCI volume increases, more females, more patients with New York Heart Association class IV heart failure, and more patients with higher bleeding risk are selected to undergo radial PCI. Operators also perform more multi-vessel PCIs and technically complex PCIs as they gain experience with radial interventions. The last frontier of the learning curve is generally the STEMI patient, who will be discussed in more detail later in this chapter.
Data regarding radiation exposure with radial versus femoral procedures have been mixed.31-33 Overall, it appears that operators and patients get higher radiation exposure with radial procedures compared with femoral procedures, but this improves as operators advance through their learning curve.34 In fact, one of the biggest factors of radiation exposure for either a radial or femoral operator is procedural volume. In a radiation substudy of the RIVAL trial, there was a nominal overall increase in radiation dose with radial versus femoral access, but this difference was observed only in lower-volume centers and operators.35 Medium- and high-volume centers showed no significant difference, and high-volume centers had the lowest radiation dose irrespective of which access site they used.
All operators should do what they can to minimize radiation exposure. In addition to the usual steps such as using standard shielding, maintaining distance, and lowering the frame rate, certain radial-specific devices, including a radial radiation protection board,36 a radiation shield over the radial sheath insertion site,37 and draping the patient’s pelvis with a lead shield,38 should be strongly considered.
While bleeding and vascular complications with the radial approach are rare, they can occur. Hematoma of the forearm is generally easily controlled with a brief course of manual compression. Wrapping the forearm with an Ace bandage or a self-adherent elastic wrap for 15 to 30 minutes following manual compression can prevent recurrence, but close attention needs to be paid to make sure that the hematoma is not expanding, in which case manual compression needs to be resumed. A blood pressure cuff may also be utilized, inflated to systolic pressure and then gradually released over time. In all cases where there is circumferential pressure around the arm, venous stasis can occur. A brief hiatus to allow perfusion before continued compression may be necessary. Compartment syndrome is a poorly managed hematoma that leads to hand ischemia. If radial patients are being closely tended to in recovery, compartment syndrome should never occur.
Both pseudoaneurysms and arteriovenous fistulas can occur in the radial artery, but are rare. A pseudoaneurysm is usually easily treated by having patients wear a hemostatic device over the radial artery for up to an hour. If unsuccessful, a longer duration may be necessary or a thrombin injection could be considered. Other complications, including spasm, vessel dissection or perforation, and radial artery occlusion will be specifically addressed below.
The entire cardiac catheterization laboratory needs to be educated about the radial approach so that procedures run smoothly and safely from the time of the patient’s arrival to his or her departure. In the pre-procedural area, intravenous (IV) tubes should not be placed near the wrist, and an antecubital IV should be placed if a right heart catheterization (RHC) is anticipated (see below). Groins will often be prepped, particularly earlier in the learning curve.
Most patients are suitable candidates for radial access. Some relative contraindications to consider are the presence of severe Raynaud’s phenomenon, presence of a dialysis arteriovenous fistula, and history of a left internal mammary artery (LIMA) bypass graft where the left radial artery has also been used as a bypass conduit. In this situation, the LIMA will have to be accessed from the right radial artery, which is challenging, though not impossible. Whether to also forgo the radial approach on patients who have an abnormal modified Allen’s or Barbeau test is controversial. There are no data demonstrating that performing a modified Allen’s or Barbeau test to evaluate the patency of the ulnopalmar arch predicts hand ischemia,39 but many operators, particularly in the United States, still prefer to do it. Compared to the modified Allen’s test, the Barbeau test has been found to be more sensitive40 and is also typically used in a reverse fashion when assessing for patent hemostasis (see below).
Once in the procedural room, either the right or left arm will be prepared for access. The right arm is generally more convenient, but there are advantages to the left arm.41,42 The left subclavian artery is often less tortuous than the right subclavian/innominate, particularly in patients who are older than 75 years of age and shorter than 165 cm.43 In addition, the curves taken by the catheter more closely mimic those seen when coming from the groin. As a consequence, operators may find the procedures easier and the learning curve shorter when using the left arm. There are also data to suggest that radiation exposure is less from the left arm. Regardless of the preferred side, becoming facile at left arm setup is a must for any lab. The left arm will be needed for coronary artery bypass grafting (CABG) cases and crossover if access or engagement from the right radial artery fails.
For left arm procedures, the left radial artery is typically accessed from the left side of the patient. Then the operator returns to the right side of the patient, where she or he is accustomed to standing and driving the table. The left arm is brought up on the patient’s body and secured in place. Various methods have been employed for securing the arm, but a high arm board and some blankets usually suffice. The wrist then sits at about the level of the left groin.
For radial access preparation, the arm is placed on a board that will allow the arm to be brought to the patient’s side during the procedure, or up on the body in case of left wrist access. The wrist is slightly hyperextended, either with a rolled towel or specialized wrist splint (Fig. 22-2). For new radial operators, the groin should be prepped and ready for access, so that crossover does not add to the burden of learning a new skill. However, as proficiency grows and crossover decreases, consideration should be given to discontinuation of groin prep, which is rarely needed and only adds to staff preparation time. For right arm procedures, there should be a board distal to the arm that extends from the table and provides a working surface, as it is often not feasible to work on the patient’s body, as is usually done from the femoral approach. Finally, the patient can be draped with a specialized radial drape, or a neck drape can be used to cover the arm in addition to the usual femoral drape (Fig. 22-3).
Prior to starting the case, take a moment to make sure that the patient is comfortable and reasonably sedated.44 Anxious patients are more prone to spasm, and the key to avoiding spasm is prevention. The optimal site for radial access is approximately 2 cm proximal to the radial styloid process (Fig. 22-4). There is a tendency for new operators to creep distally, but while the radial pulse may be stronger at the level of the styloid process, the radial artery is more likely to turn or give off branches in this area, making access more difficult. Once the proper location is identified, a small amount of lidocaine should be administered. Only about 1-2 mL is needed (Fig. 22-5), and too much may obscure the pulse.
There are 2 techniques for accessing the radial artery. The first is the modified Seldinger technique, which uses a short micropuncture needle, and the second is the Seldinger technique, which uses an angiocath needle. The modified Seldinger technique involves making an anterior wall stick and, once in the vessel, slightly adjusting the needle’s position for the best blood return possible prior to advancing the wire. The Seldinger technique involves puncturing the anterior wall, which results in blood return, and then continuing the puncture through the posterior wall until the blood return stops (Fig. 22-6). This ensures that the needle catheter is deep enough when the needle is removed. After removal of the needle, the catheter is pulled back at a superficial angle until there is blood return, at which point the wire is advanced (Fig. 22-7). With this latter technique, there are no other adjustments of the needle catheter—once it is in, it is in. While either technique is safe and effective, the Seldinger technique may be easier, particularly for new operators.45
For access, the needle is held at a 30° angle, and once the pulse is identified, the needle should be advanced gently, but definitively. If the artery is missed, prior to pulling back on the needle, determine if the pulse is more medial or lateral. Then, withdraw the needle just to the surface of the skin and redirect, preferably without making a new puncture in the skin. Rather than manual palpation, another option is ultrasound. Some operators like to use it when they are having difficulty hitting the artery or the pulse is weak, whereas others use it routinely. When used routinely, ultrasound has been shown to decrease the number of attempts and time to access.46 Another trick to use if the pulse is weak is to have someone occlude the ulnar artery or the radial artery distal to the access site to increase the force of the pulse.
The hydrophilic sheath is one of the advances in radial artery equipment that has improved the procedure since the 1990s. Hydrophilic sheaths have been shown to reduce spasm, but the length of them has not. Since the sheath has the largest outer diameter of anything being put in the artery, minimizing its length whenever possible seems prudent. Because of its hydrophilicity, a skin nick is rarely needed. Instead, the sheath is advanced directly through the skin while being rotated side to side (Fig. 22-8). If the skin is tough, a small nick can be made. However, the sheath can slide easily in and out of the skin, so the nick should be kept to a minimum. Once the sheath is in place, some operators like to secure it with a Tegaderm dressing to keep it from slipping out. There should not be any significant pain or resistance when advancing the sheath. If there is, investigate before advancing further. Perhaps the artery is too small for the sheath, or there is spasm or heavy calcification.
Sheath size should be kept to a minimum. Larger sheaths, particularly in relation to the size of the radial artery, have been implemented as one of the causes of radial artery occlusion.47 For diagnostic cases, a 5-Fr system is generally sufficient and some operators use 4-Fr. Newer thin-walled sheaths allow for passage of 6-Fr equipment while maintaining a 5-Fr outer diameter, or 5-Fr equipment while maintaining a 4-Fr outer diameter. Another advantage to the thin-walled sheath is that it can minimize sheath exchanges. Prior to their advent, an operator would start with a 4-Fr or 5-Fr sheath for the diagnostic angiogram, but if the case needed to go to PCI, the operator either had to do a 5-Fr PCI, which had equipment limitations, or upsize to a 6-Fr sheath. Now, a 6-Fr thin-walled sheath can be used for the entire case. Most PCIs can be done with a 6-Fr system. In rare circumstances, an operator might want to upsize to a 7-Fr or 8-Fr. Few patients, especially women, can safely accommodate that size sheath in their radial artery. As an alternative, there is a now a 7-Fr thin-walled sheath (with a 6-Fr outer diameter) or there are sheathless systems. Sheathless systems eliminate the sheath and drop the French size down to the outer diameter of the guide, which is ~2-Fr smaller than the outer diameter of the traditional sheath. The sheathless system, however, requires a smooth transition at the tip of the guide so that it can be advanced from the skin into the artery with minimal trauma. There are limited dedicated sheathless guides or one can be made by putting a smaller introducer within the guiding catheter.48